[GadgetKen]

The number of sims listed as standby are the number of lines that can be monitored for receive at the same time. On some phones it equals the number of sims, on a few multi-sim phones, it may be less.

If you are receiving a phone call on any of these standby sims, then it would ring and you would answer. However, some phones only have bluetooth on one of these sims (in the case of my dual sim MFU v200 it's on both, on the case of this quad sim phone it is only advertised as bluetooth on line one). Answering from the handset without bluetooth would be on any of these lines. Likewise with a wired handset.

For placing phone calls, there are multiple send buttons on the phone. If I bring up my phonebook (a composite of all sims with a sim card number indicator next to each phone number), I can then specify which sim I want to dial the call. Or I can manually dial a number and then press the send 1/2 or send 3/4 button to specify I want to call with one of those sims (and then specify which of those 2 sims I want to dial from a menu either on the touchscreen or with the directional keypad).

Note that not all sims may work in all countries, and rates will vary by country used. In the US, all 4 sims would be active for me (although roaming rates using the Digicel card would be high). When I am in Grand Cayman early next year, the Digicel and Ekit sims would be cheapest for calls, while the AT&T/Jolt and T-Mobile/Tuyo would only work in emergency call mode since they are prepaid sim chips without roaming in that country.